Fish tank



FIG. 1 is a front perspective view of the fish tank showing my new design;

FIG. 2 is a front plan view thereof;

FIG. 3 is a back plan view thereof;

FIG. 4 is a left plan view thereof;

FIG. 5 is a right plan view thereof; and,

FIG. 6 is a downward plan view thereof.

The broken line showing in the drawings is included for the purpose of illustrating unclaimed portions of the fish tank and forms no part of the claimed design. 

CLAIM The ornamental design for a fish tank, as shown and described. 